U.S. patent application number 11/570634 was filed with the patent office on 2008-02-21 for set and forget exhaust controller.
This patent application is currently assigned to OY HALTON GROUP LTD.. Invention is credited to Andrey V. Livchak, Derek W. Schrock.
Application Number | 20080045132 11/570634 |
Document ID | / |
Family ID | 35782303 |
Filed Date | 2008-02-21 |
United States Patent
Application |
20080045132 |
Kind Code |
A1 |
Livchak; Andrey V. ; et
al. |
February 21, 2008 |
Set And Forget Exhaust Controller
Abstract
A controller automatically determines drive signals by testing
an exhaust system, either immediately after installation or at
selected times thereafter, to determine the drive signal values
that correspond to each of one or more selected flow rates. The
drive signals are stored. Thereafter, the controller uses the
stored values of drive signals to control the exhaust system. This
avoids problems with real time control such as drift or failure of
sensors and such which are very common in commercial exhaust
installations.
Inventors: |
Livchak; Andrey V.; (Bowling
Green, KY) ; Schrock; Derek W.; (Bowling Green,
KY) |
Correspondence
Address: |
PROSKAUER ROSE LLP
1001 PENNSYLVANIA AVE, N.W.,
SUITE 400 SOUTH
WASHINGTON
DC
20004
US
|
Assignee: |
OY HALTON GROUP LTD.
Vantaa
FI
01510
|
Family ID: |
35782303 |
Appl. No.: |
11/570634 |
Filed: |
June 21, 2005 |
PCT Filed: |
June 21, 2005 |
PCT NO: |
PCT/US05/21969 |
371 Date: |
June 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60581751 |
Jun 22, 2004 |
|
|
|
Current U.S.
Class: |
454/61 |
Current CPC
Class: |
F24C 15/2021
20130101 |
Class at
Publication: |
454/061 |
International
Class: |
F24F 7/007 20060101
F24F007/007 |
Claims
1. A controller for an exhaust device, comprising: a programmable
controller module (PCM) having a memory storing at least one value
corresponding to a flow rate; said PCM having an input configured
to, at a first time, receive a signal indicating a flow rate
measurement; said PCM having an output configured to output a drive
signal to control a flow rate of an exhaust system; said PCM being
configured to adjust, at said first time, a drive signal to adjust
a flow rate of an exhaust system responsively to said signal
indicating a flow rate measurement until it substantially
corresponds to said at least one value corresponding to a flow
rate; said PCM being configured to store, at said first time, a
value of said drive signal in said memory; said controller being
configured to control, at a second time, a flow rate of said
exhaust system according to said drive signal value stored in said
memory.
2. A controller as in claim 1, wherein: said PCM is configured to
store multiple values each corresponding to a respective flow rate
and to determine, at said first time, multiple values of said drive
signal, each corresponding to a respective one of said multiple
values each corresponding to a respective flow rate; each of said
drive signals corresponding to a load condition; said PCM is
further configured to receive a signal indicating a load condition
and to output a corresponding value of said drive signal
responsively thereto.
3. A controller for exhaust systems, comprising: a control unit
storing one or more flow values; said control unit being configured
to, at a set up time, adjust a flow rate in response to a flow
measurement signal and thereby to automatically determine drive
signals to each of said one or more flow values; the control unit
being configured to store the one or more drive signals and
thereafter use them to control a flow rate of an exhaust system.
Description
BACKGROUND
[0001] One of the problems with installing exhaust hoods in
industrial, commercial, and large residential systems is adjusting
the flow rate of each hood so that a minimum volume of air is
exhausted to ensure capture, containment, and removal of effluent.
The performance of a hood, however, is very variable depending upon
how it is installed. Often, unforeseen adjustments made in the size
and length of ducting and other variables established during
installation make it impossible to select an exhaust blower
configuration which will deliver a desired exhaust flow once a hood
is installed. Because of the cost of unnecessarily high exhaust
capacity, it is important to establish a desired exhaust flow upon
installation.
[0002] Currently, one way of dealing with this problem is for an
installer to perform a flow measurement and make adjustments to a
fan system to establish a desired flow. However, such field
measurements and procedures are time consuming and subject to error
and common sloppiness.
SUMMARY
[0003] Briefly, A controller automatically determines drive signals
by testing an exhaust system, either immediately after installation
or at selected times thereafter, to determine the drive signal
values that correspond to each of one or more selected flow rates.
The drive signals are stored. Thereafter, the controller uses the
stored values of drive signals to control the exhaust system. This
avoids problems with real time control such as drift or failure of
sensors and such which are very common in commercial exhaust
installations. A variable frequency motor drive can be used, for
example. The system may be used in combination with real time
control. If a failure of the real time control system is detected
such as by detecting out-of-range sensor or drive signal (for
feed-forward control) values, the controller can default to the
stored drive signal values.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is an illustration of an exhaust hood with a flow
control system.
[0005] FIG. 2 is a more detailed illustration of a control system
shown in FIG. 1.
[0006] FIG. 3 is a flow chart illustrating a control method.
[0007] FIGS. 4A and 4B illustrate alternative details of a simple
feedback or feed-forward control loop with the escape.
[0008] FIG. 5 illustrates a control method which is an alternative
to the one of FIG. 3.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0009] FIG. 1 illustrates an exhaust hood 145 with a flow
controller/drive unit 105. A fan 310 draws air through a duct 180
that leads away from recess 135 of the exhaust hood 145. A filter
115 separates the recess 135 from the duct 180 and causes a
pressure drop due to the known effect of grease filters in such
applications. A pressure sensor 140 measures a static pressure
which can be converted to a flow rate based on known techniques due
to the flow resistance caused by the filter 115. A differential
pressure reading may also be generated using an additional pressure
sensor 142 or a differential sensor (not shown separately) with
taps upstream and downstream of the filter.
[0010] Instead of a filter, reference numeral 115 may represent an
orifice plate or other calibrated flow resistance device and may
include a smooth inlet transition (not shown separately) to
maximize precision of flow measurement by means of pressure loss.
Instead of pressure sensors 140 may represent a flow measurement
device such as one based on a pitot tube, hot wire anemometer, or
other flow sensor. The sensor 140 may be replaceable since, as
discussed below, it is used only once or intermittently so that
replacement would not impose an undue burden.
[0011] FIG. 2 illustrates details of the controller/drive unit 105
according to an embodiment of the invention. A fan 31 1, which may
correspond to the fan 310 of FIG. 1, is driven at a selected speed
by a variable speed drive 300. The latter may be an electronic
drive unit or a mechanical drive with a variable transmission or
any other suitable device which may receive and respond to a
control signal from a controller 320. The latter is preferably an
electronic controller such as one based on a microprocessor. The
controller 320 accesses stored data in a memory 330. The memory may
contain calibration data such as required to determine flow rate
from pressure readings or anemometer signals (illustrated generally
as a transducer 340 and flow sensor 350). In addition, the memory
330 may also store a predetermined flow rate value at which the
associated exhaust hood 145 (See FIG. 1) is desired to operate.
Thus, the controller 320 can determine a current flow rate and
compare it to a stored value and make corresponding adjustments in
fan speed (or otherwise control flow, such as by means of a
damper).
[0012] The memory 330 also stores fan speed value so that once a
particular fan speed is determined to achieve a desired flow rate
(e.g., one predetermined value stored in memory 330), the
associated fan speed can be stored in memory 330 and used to
control the fan after that. In this way, the required fan speed
need not be determined, as in common feedback control, each time
the system operates. This is desirable because the accuracy of flow
measurement devices is notorious for its tendency, particularly in
dirty environments such as exhaust hoods, to degrade over time.
[0013] FIG. 3 illustrates a control procedure for use during set-up
when a hood is installed. First a command is issued at step S90 to
start the exhaust hood. In step S95, it is determined whether a fan
speed has been determined by a configuration procedure. If not,
control proceeds to step S20. In step S20 the fan is started and a
flow rate measurement is made in step S30. The flow rate is
compared with a value stored in the memory 330 at step S40 and if
it is equal (assumed within a tolerance) to the predetermined
value, control proceeds to step S80. If the flow rate is unequal it
is determined if the flow rate is higher at step S50 and if so, the
fan speed is increased at step S70 and if not, the fan speed is
decreased at step S60. After step S60 or S70, the comparison is
repeated at step S40 until the predetermined and measured flow
rates are substantially equal.
[0014] In step S80, the value of the fan speed (or corollary such
as a drive signal) is stored in the memory 330. In addition, step
S80 may include the step of setting a flag to indicate that the
procedure has been run and a desired fan speed value stored. The
stored value is retrieved at step S100 and applied to operate the
fan at step S105. If the configuration process S20 to S80 had been
run already, the flow would have gone from step S95 to step S100
directly resulting the exhaust hood operating at the fan speed
previously determined to coincide with the desired flow.
[0015] In another embodiment, the memorized driver signal is used
as a default driver signal. Input control signals are permitted to
supersede the default driver control when the difference between
the desired level exceeds the default by a specified margin. The
iterative control process is encapsulated in step S115. Iterative
control may be according to any suitable real-time (feed-forward or
feedback) control method, for example ones discussed in U.S. Pat.
No. 6,170,480, hereby incorporated by reference as if set forth in
its entirety, herein. In step S115, if the inputs of a feedback
control signal lie outside a specified range, the default drive
signal stored in the memory is used. Detection of an input range
outside the specified range causes control to escape E10 and return
to the default drive signal. If the feedback control signal(s) lie
within the specified range, feedback control is used to determine
the drive signal.
[0016] FIGS. 4A and 4B illustrate the possible details of a simple
feedback or feed-forward control loop with the escape. Step S105 is
the same as the similarly numbered step of FIG. 3. FIG. 4A
corresponds to a feedback control method. A stored drive signal is
applied by default to drive the fan. Then at step S135 the real
time conditions are detected and converted to values or levels that
can be compared with stored values or signal levels defining a safe
operating window. At step S140, it is determined if the detected
real time conditions are within the safe window. If they are,
control proceeds to step S150 and if not, the escape path E10 is
taken and stored default drive signals are applied. In step S150, a
feedback setpoint is compared to the detected real time values of
the feedback control signal and adjusted accordingly as indicated
by steps S155 and S145, respectively whereupon control proceeds
back to step S135.
[0017] FIG. 4B corresponds to a feed-forward control method. Step
S105 is the same as the similarly numbered step of FIG. 3; a stored
drive signal is applied by default to drive the fan. Then at step
S136 the real time conditions are detected and converted to values
or levels that can be compared with stored values or signal levels
defining a safe operating window or used to generate a drive
signal, at step S170, using a feed-forward control method.
[0018] Feed-forward control is not described here, but feed-forward
control, in general, is conventional. An example of feed-forward
control applied to a complex ventilation problem (among other
things) is described in U.S. patent Ser. No. 10/638,754, entitled
"Zone control of space conditioning system with varied uses" which
is hereby incorporated by reference as if fully set forth in its
entirety herein.
[0019] At step S180, the detected signals or the predicted drive
signal are compared with values defining an allowed window and
determined to acceptable or not. In other words, S180 may compare a
drive signal value to an allowed range stored in a memory of the
controller or it may compare the real time condition signal to
specified values stored in a controller memory, similar to step
S140 of FIG. 4A. Detection of a value outside the specified range
causes control to escape E10 and return to the default drive
signal. Otherwise, the predicted drive signal is used to drive the
exhaust system and control returns to step S135.
[0020] FIG. 5 illustrates another control procedure for use during
set-up when a hood is installed. First, as in the embodiment of
FIG. 3, a command is issued at step S90 to start the exhaust hood.
In step S95, it is determined whether a fan speed has been
determined by a configuration procedure. If not, control proceeds
to step S200. In step S200, an index (counter value) n is
initialized whose value will span the number of different control
conditions to be covered by the instant procedure.
[0021] In step S20 the fan is started and a first stored value of a
desired flow rate is read. Each of N flow rate values F.sub.n
corresponds to a respective desired flow rate associated with
particular one of N operating conditions. Each F.sub.n is stored in
a controller memory. A flow rate measurement is made in step S30
and compared with the current F.sub.n (the value of F.sub.n
corresponding to the index value n initialized in step S200. If it
is equal (assumed within a tolerance) to the predetermined value,
control proceeds to step S215. If the flow rate is unequal it is
determined if the flow rate is higher at step S250 and if so, the
fan speed is increased at step S70 and if not, the fan speed is
decreased at step S60. After step S60 or S70, the comparison is
repeated at step S240 until the current flow value F.sub.n and
measured flow rates are substantially equal.
[0022] In step S215, the value of the fan speed (or corollary such
as a drive signal) drive signal is stored in the n.sup.th one of N
memory locations 330. In addition, step S215 may include the step
of setting a flag to indicate that the procedure has been run and
the desired fan speed values stored when n reach N. The value of
the index n is incremented in step S220 and if all values of
F.sub.n have not yet been set, control returns to step S225.
Otherwise control goes to step S240. Conditions are detected in
step S240 and the associated stored value of the driver signal
determined in step S245. The determined drive signal is then
applied in step S105 and control loops back to step S240.
[0023] In another embodiment, the memorized driver signal is used
as a default driver signal. Input control signals are permitted to
supersede the default driver control when the difference between
the desired level exceeds the default by a specified margin. The
iterative control process is encapsulated in step S115. Iterative
control may be according to any suitable real-time (feed-forward or
feedback) control method, for example ones discussed in U.S. Pat.
No. 6,170,480, hereby incorporated by reference as if set forth in
its entirety, herein. In step S115, if the inputs of a feedback
control signal lie outside a specified range, the default drive
signal stored in the memory is used. Detection of an input range
outside the specified range causes control to escape E10 and return
to the default drive signal. If the feedback control signal(s) lie
within the specified range, feedback control is used to determine
the drive signal.
[0024] In step S240, the conditions detected may be, for example,
the fume load predicted from one or more inputs. For example, the
time of day (a restaurant that cooks according to a particular
schedule) can be used to determine the fume load. Another input may
be an indication of whether a protected fume source, such as a
kitchen appliance, has been turned on and for how long. The fuel
consumption rate may also be used. Other kinds of detection
mechanisms may also be employed, such as described in U.S. Pat. No.
6,899,095 entitled "Device and method for controlling/balancing
flow fluid flow-volume rate in flow channels," hereby incorporated
by reference as if fully set forth in its entirety herein. Expected
flow values for the following exhaust conditions are listed here
for an example: (1) full load; (2) intermediate load; (3) idle; (4)
initialization (e.g., burners turned on, but no cooking yet) in
winter; (5) initialization in summer. The reason summer and winter
(or it could be based on temperature) may be different is that the
heat liberated by a heat source may be undesirable in summer but
more acceptable during winter time.
[0025] The sensors used for feedback or feedforward control may
include any of a variety of types which may be used to prevent
escape of pollutants from an exhaust hood. The flow sensors used
for determining drive signals associated with desired flow rates
may be any type of flow sensor. Preferably, the flow sensor is one
which is robust and which is not overly susceptible to fouling. One
of the fields of application is kitchen range hoods, which tend to
have grease in the effluent stream. For example, static pressure
taps with pressure transducers in the exhaust duct may provide a
suitable signal.
* * * * *